/Engine/Plugins/Online/OnlineSubsystem/Source/Public/Interfaces/OnlineGroupsInterface.h
Get cached user membership information (if it exists). This retrieves which groups they are members of. If UserId is the ID of the context user, then this list will include groups to which the user has been invited (use JoinGroup to accept, LeaveGroup to decline) or groups they have petitioned but haven't received a response for yet.
[TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< const [IUserMembership](API\Plugins\OnlineSubsystem\Interfaces\IUserMembership) > GetCachedUserMembership ( const [FUniqueNetId](API\Runtime\CoreOnline\Online\FUniqueNetId) & ContextUserId, const [FUniqueNetId](API\Runtime\CoreOnline\Online\FUniqueNetId) & UserId )